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The effects of 'stress fatigue' on performance in a simulated driving situation.

Fifty four male subjects were assigned to three equal groups and tested in a simulated driving device. The following measures were obtained for each subject: tracking error, speed maintenance, reaction time, and vigilance. In the contingent shock group (stress group) subjects received an electrical shock when errors were committed on one of the tasks. In the second group subjects received random shock with no relationship between shock and performance. The subjects in the control group received no shock. Test sessions in the device were six hours in duration. No significant differences were found between groups on tracking performance. However, significant differences existed between hours with the contingent shock group showing significantly more tracking error during the last two hours of the test session than during the earlier hours. On the subsidiary tasks, it was found that no significant differences existed between groups on reaction time. However, differences between trials were found with subjects in the contingent group showing significantly slower reaction time during the last two hours of the session. On the meter vigilance task, subjects in the contingent group missed significantly more signals than subjects in the other groups. Also, on the speed maintenance task the error level for the contingent group was higher than that shown by the other groups. Results are discussed in terms of Crawford's (1961) concept of stress fatigue. Findings support the concept that stress brings about an emotional arousal which may interfere with performance on tasks such as driving. (Grant No. T01- OH-00002)